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Scientists Retrieve Proteins From Dinosaur Bone

In a retrieval once thought unattainable, scientists have recovered and identified proteins in a bone of a well-preserved Tyrannosaurus rex, a dinosaur that lived and died and was fossilized 68 million years ago.

The scientists, who announced the discovery today, said the success with advanced research techniques opened the door for the first time to the exploration of molecular-level relationships of ancient, extinct animals, instead of just relying on their skeletal remains.

Dinosaur fossil hunters are planning nine expeditions this summer to search wide and deep for more specimens as promising candidates for similar tests. A few large dinosaur bones already in laboratories may be examined for surviving traces of organic matter.

The earliest previously identified ancient proteins were from mammoths that died about 300,000 years ago. The oldest confirmed samples of DNA — a more direct bearer of information of molecular evolution, but also more degradable — have come from Neanderthals that lived 30,000 to 50,000 years ago. The extraction of DNA would be necessary for studies in dinosaur genetics and for cloning experiments.

Repeated analysis of the T-rex proteins, the researchers said, uncovered new evidence of a link between dinosaurs and birds, a widely held but contentious hypothesis. Three of the seven reconstructed protein sequences were closely related to chickens. The scientists resisted being drawn into speculation on the likely taste of a T-rex drumstick.

Two research teams are reporting the findings in Friday’s issue of the journal Science. The principal investigators discussed the results with reporters in a teleconference on Wednesday.

Speaking of the doubts she had going into the work, Mary Higby Schweitzer of North Carolina State University, leader of one of the groups, said, “We had always assumed that preservation does not extend to the cellular level” in ancient fossils.

Dr. Schweitzer described several different tests that were conducted on soft tissues found deep inside a tyrannosaur’s femur, or thighbone, excavated in eastern Montana. She reported the surprising tissue discovery two years ago.

Though barely detectable, proteins of collagen 1, the main organic component of bone, were separated and examined. Fragments, or peptides, of the protein were pieced together into strands of the seven sequences. Three of these reacted with antibodies to chicken collagen. Two others appeared possibly related to living creatures, a frog and a newt.

A team headed by John M. Asara of the Harvard Medical School and Beth Israel Deaconess Medical Center in Boston said its independent tests confirmed the presence of proteins in the tissue.

The researchers submitted samples of the material extracted by Dr. Schweitzer to an examination by mass spectroscopy, which breaks down material to its component parts to determine its mass and chemical makeup. The technology is applied in medical research to analyzing more precisely the nature of disease-causing agents.

Dr. Asara said the most difficult part of the research was making sure all of the “brown gritty contaminants” were separated out of the specimen. After several steps in the purification process, the protein fragments were separated from one another, measured for mass and joined in seven separate strings of amino acid. Five of the seven sequences were proteins of collagen 1.

Lewis Cantley, a Harvard biology professor on the team, said he was satisfied that the findings were “unlikely due to contamination.”

In a news release from Harvard, Dr. Cantley said, “Basically, this is the breakthrough that says it’s possible to get sequences beyond one million years,” which had been thought of as the absolute time barrier for the preservation of organic matter in animal remains. In the fossilization process, minerals replace the constituents of bones, turning them to stone.

Similar tests by Dr. Asara’s team also isolated and pieced together more than 70 protein fragments from a mastodon estimated to be from 160,000 to 600,000 years old. The researchers said this provided further evidence of the staying power of ancient protein.

“We can now start to create relationships between extinct and living organisms,” Dr. Asara said, adding that the T-rex tests supported the idea “that birds are derived from dinosaurs or are closely related.”

The huge tyrannosaur thigh was discovered in 2003 by John R. Horner of Montana State University, a longtime dinosaur paleontologist better known as Jack. It was excavated at a depth of 60 feet in the Hell Creek Formation, a dinosaur-rich bed of sedimentary rock underlying much of Montana and Wyoming.

Dr. Schweitzer, a biologist affiliated also with Montana State, cut into the thick bone and recovered the soft tissues, including blood vessels and possibly cells that, she said at the time, “retain some of their original flexibility, elasticity and resilience.” This had never been found in a dinosaur before and prompted the investigations into the nature of the organic matter.

Mr. Horner suggested that the size of the bone and the depth of its entombment accounted for the unusual preservation of the tissues. Thick bones, he said, afford interior matter more protection from environmental degradation. Another factor was that this particular dinosaur was buried in a virtually oxygen-free setting very soon after death. The depth also may have insulated it over time.

Mr. Horner said paleontologists should look for other candidates for soft tissue retrieval among remains of the largest dinosaurs resting under tens of feet of rock. Such excavations, he conceded, will not be easy. But this will be the quest of more than 100 fossil hunters fanning out this summer in the American West and as far away as the Gobi Desert of Mongolia.